Background: The benefits of radiotherapy for cancer have been well documented for many years, but many patients treated with radiation develop adverse effects. This study analyzed the current research into the biological basis of radiotherapy-induced normal tissue damage.
Methods: Using the PubMed and EMBASE databases, articles on adverse effects of radiotherapy on normal tissue published from January of 2005 through May of 2012 were identified. Their abstracts were reviewed for information relevant to radiotherapy-induced DNA damage and DNA repair. Articles in the reference lists that seemed relevant were reviewed with no limitations on publication date.
Results: Of 1751 publications, 1729 were eliminated because they did not address fundamental biology or were duplicates. The 22 included articles revealed that many adverse effects are driven by chronic oxidative stress affecting the nuclear function of DNA repair mechanisms. Among normal cells undergoing replication, cells in S phase are most radioresistant because of overexpression of DNA repair enzymes, while cells in M phase are especially radiosensitive. Cancer cells exhibit increased radiosensitivity, leading to accumulation of irreparable DNA lesions and cell death. Irradiated cells have an indirect effect on the cell cycle and survival of cocultured nonirradiated cells. Method of irradiation and linear energy transfer to cancer cells versus bystander cells are shown to have an effect on cell survival.
Conclusions: Radiotherapy-induced increases in reactive oxygen species in irradiated cells may signal healthy cells by increasing metabolic stress and creating DNA lesions. The side effects of radiotherapy and bystander cell signaling may have a larger impact than previously acknowledged.
From the Department of Plastic and Reconstructive Surgery, The University of Texas M. D. Anderson Cancer Center.
Received for publication October 3, 2012; accepted June 7, 2013.
Disclosure: The authors have no financial interests to declare in relation to the context of this article.
Steven J. Kronowitz, M.D., Department of Plastic and Reconstructive Surgery, The University of Texas M. D. Anderson Cancer Center, Unit 1488, P.O. Box 301402, Houston, Texas 77230-1402, firstname.lastname@example.org